Pyrethroids are useful as insecticides. Among the proprietary pyrethroids there may be mentioned for example fenvalerate which has wide application in agricultural fields. These compounds are further characterized as having high activity against insects and low mammalian toxicity.
Chemically, these compounds can be readily prepared from (+)-trans-chrysanthemic acid, i.e. 2,2-dimethyl-3-(2-methylpropenyl)-cyclopropanecarboxylic acid. It has been found that there is a close correlation between the chirality of this molecule and its insecticide activity. Among the four optical isomers of chrysanthemic acid exhibiting insecticidal activity, the most effective isomer is found to be the (+)-trans isomer. The next most effective isomer is the corresponding (+)-cis isomer. In contrast, the (-)-trans and the (-)-cis isomers are almost ineffective as insecticides. On the other hand, the naturally occurring chrysanthemic acid has the (+) (lR)-trans configuration.
The present invention relates to Cu complexes of new bis-oxazolines useful in the catalytic cyclopropanation of trisubstituted and unsymmetrical cis-1,2-disubstituted olefins exhibiting high enantoselectivity. The resulting cyclopropanated products are useful in the production of the desired pyrethroids and their derivatives.